Electrogravimetry Impedance Measurements

The usual derivation based on the linearization procedure allows calculation of the electrochemical impedance and the M/U transfer function. Two types of behavior occur, depending on whether the average mass of the electrode changes continuously with time. 

When the mass increases or decreases (e.g., for deposition or dissolution of a metal) at a constant current, the low-frequency limit of M/U tends to infinity. 

The simultaneous measurement of the impedance and mass/potential transfer function leads to new information on the kinetics of the processes involved. It may lead to chemical identification of the species involved in the intermediate reaction steps by allowing the atomic masses of the adsorbed intermediates of the multistep reaction mechanisms to be estimated. 

1 Derive the steady-state concentration gradient corresponding to equation (14.55). 

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AC electrogravimetry consists in the simultaneous measurements of the electrochemical impedance and the mass/potential, or electro-gravimetric, transfer function. Impedance measurements are already well documented in the literature hence, in this text, only the electrogravimetric transfer function measurement will be described. It uses a fast QCM whose general concepts are first given below. 

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